The orthodontic procedures for straightening teeth today involves the placement of brackets on the external of the teeth with an adhesive and connecting a force, an arch wire, to the brackets to move the teeth. Hooks have been secured to the brackets and arch wires for use as an anchoring device for intramaxillary or intermaxillary springs, elastomeric modules, elastics, or ligature wires. In the treatment of dentofacial deformities where orthognathic surgery has moved one or both jaws the jaws are often postoperatively ligated together using intermaxillary ligature wires tied to orthodontic hooks to immobilize the jaws, allowing healing in the new position.
Hooks have been secured to arch wires by welding or silver soldering as described in U.S. Pat. No. 3,508,332 at column 1, lines 35 and 36. If the manufacturer places the hooks it is difficult for the hooks to be attached to an arch at locations best suited for a particular patient. A great amount of skill is required of the orthodontist to place the hooks on an arch wire without inadvertently annealing the arch wire. An arch which becomes annealed loses Its ability to transmit orthodontic forces effectively to the teeth to which the brackets carrying the arch are bonded. The movement of soldered or electro-welded arch wires hooks which have been in the mouth is further complicated by the fact the wire must be absolutely clean in order to place a new hook. Cleanliness is difficult to assure for an arch wire that has been in the mouth any appreciable length of time.
Alternately, hooks have been mounted on caps engage able with orthodontic brackets, as described in U.S. Pat No. 3,391,461 at column 2, lines 24 and 25. A principal difficulty with such a hook mounting is that it is necessary to hold the cap in place on the bracket while bending the retaining tabs to engage the bracket, which also may exert force on the bracket. Bending of the tabs to remove the hook mounting may additionally exert force on the bracket.
Hooks have been attached to arch wires by small set screws as found in U.S. Pat. No. 3,158,934 and U.S. Pat. No. 4,639,219. The set screws tend to loosen in the mouth.
Another method has been to crimp the hook to the arch using a crimping tool. Even when the hooks are crimped they tend to slide along the arch wire.
In U.S. Pat. No. 4,797,095 an intricate removable hook attaches to the arch wire where it also embraces the bracket.
The hook which most resembles the present invention is the Kobyashi tie wire which is a ligature tie wire, usually 0.012 inches in size, tack welded approximately 4 mm from its closed end. The closed-end forms a hook as it is tied as a normal ligature wire. The tied end forms a pigtail which has to be cut and pushed under the arch wire for patient comfort. The tucking of the pigtail often loosens the hook and the cut end often is bent towards the patient's cheek or lip and pokes the patent while being worm.
Recently hooks have been manufactured as an integral part of the orthodontic bracket. The disadvantage of this type of hook is the orthodontist must predict the locations hooks will be needed during treatment at the time the braces are installed. The need for hooks in certain areas usually develops during treatment and initially placing hooks everywhere may be more uncomfortable for the patient along with more difficult oral hygiene.